However, the expression levels of MHC class II transactivator (CIITA), regulatory factor X 5 (RFX5), CAMP responsive element binding protein 1 (CREB1), and nuclear transcription factor Y subunit A (NFYA), which are essential for the transcriptional activity of MHC I and MHC II, were increased following virus infection. This evidence concerns the gene RFX5 and viral infectious disease.